1. Field of the Invention
This invention relates to a milling, surfacing and polishing machine with automatic tool change, and to a corresponding tool changing device.
The invention is particularly intended for the milling, polishing and surfacing of natural or agglomerated stones, blocks of concrete, granite, marble and like materials.
2. Description of the Prior Art
There are known surfacing and polishing machines with automatic tool change, e.g. of the type marketed by THIBAUT, a company incorporated under French law, under the name "T555".
In this type of machine, the coupling of the tool is performed in the central position co-axial with the axis of rotation of the tool by means of a part called "tightening chuck" serving to tighten and eject rods with slightly tapered cones into a spindle head by means of a fastening bolt, while the positioning of the tool is carried out by the cooperating of studs fixed to the spindle head and sockets fixed to the tool.
In these known machines, the central coupling part is not visible and is rotatably driven simultaneously with the tool: this arrangement does not enable external supervision of the coupling of a tool being rotated and enlarges the spindle shaft to maintain central sprinkling.
European patent application No. 0,074,452 describes an improvement to milling heads comprising a body in which a tool -holding spindle is rotatably mounted. In the milling head body, there is mounted, rotatably and axially sliding under the action of control elements, a sleeve in which the spindle is rotatably mounted. Said sleeve comprises bayonet-type locking elements cooperating with corresponding locking elements provided on the body of an accessory.
Said body has, on its front at its periphery and outside of the sleeve, positioning and centering means susceptible of being engaged with the corresponding means provided at the periphery of the body of the accessory.
This known structure intended for the machining of metals does not have the mechanical strength required for the processing of stones and like materials, is prone to soiling and does not enable permanent supervision of the satisfactory coupling of the tool, due to the fact that the fastening means are radially internal to the assembly comprised by the spindle and the tool-holder.
French patent application No. 2,107,710 describes an automatic tool-holder replacing and aligning device, notably for milling heads with countersink on the milling carriage of a machine-tool. In this device, the fastening means are radially interior and cannot be permanently supervised. Furthermore, the fastening by screwing into a threaded central tube prone to soiling does not enable the utilisation of this device to be envisaged for the processing of stones and like materials.